In multi-tone systems, in order to maximize bandwidth utilization, and thus achieve a maximum transmission data rate, filtering sub-channel signals within a sub-channel is often required to minimize inter-symbol interference (ISI). In addition, sharp filtering of signals between sub-channels and/or complex matrix equalization is often required to minimize inter-channel interference (ICI). At high data rates, however, digital filtering is complex, costly and consumes significant amounts of power. While analog filters consume less power, using analog filters in conjunction with matrix equalization can be cumbersome, complex and costly. In particular, this is a challenge when multi-tone sub-channels are closely spaced in frequency. Furthermore, the non-linear phase responses of many sharp analog filters may further increase ISI, thereby requiring even more complex matrix equalization. There is a need, therefore, for improved analog filtering and matrix equalization in multi-tone systems.
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